JP2005128181A - Method of manufacturing aspheric optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method capable of manufacturing an aspheric optical element highly accurate as compared to elements of prior arts at a low cost, with respect to the aspheric optical element manufactured by a resin replica method by using a sphere or a flat plane substrate approximate to the aspheric optical element which is to serve as a master die. <P>SOLUTION: In the manufacturing method, a negative die 23 is prepared by the replica method using resin by using an aspheric substrate 3 having a shape in which the ruggedness is inverted with respect to the aspheric optical element which is highly precisely polished and is to serve as the master die 1. By using the method, a variation in the thickness of the resin layer 2 is reduced as compared to the case that the spherical surface is used for the substrate, and the surface precision is hardly deteriorated even when the curing contraction is caused in the resin layer 2. The replica method of adding the resin layer to the surface of the sphere or flat plane substrate by using the negative die 23 which is thus manufactured permits the manufacture of the aspheric optical element highly accurate as compared to the elements of prior arts at a low cost. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a manufacturing method of an aspherical optical element used in various measuring devices.

Conventionally, a resin replica method has been used to manufacture an aspherical optical element at low cost. In this method, the surface of the aspherical optical element polished with high accuracy, which becomes the master mold, is first treated with a release agent, and the master mold is inverted by a resin added on the spherical or flat substrate that becomes the negative matrix. A negative type is manufactured by copying the negative type, and then the negative type is used again to copy the inverted shape of the negative type onto the resin added on the spherical surface or the flat substrate. It is a method of manufacturing.
Similarly, it is a resin replica method, but there is also a case where a negative type of a reverse shape of a desired aspheric optical element is directly manufactured, and an aspheric optical element is manufactured by copying the reverse shape onto a resin on a spherical surface or a flat substrate. is there.

Also, a method of making a product substrate itself a rough aspherical surface in order to obtain high accuracy has been proposed (see, for example, Patent Document 1).
JP 63-157103 A

  When an aspherical optical element is manufactured by the resin replica method using a spherical or flat substrate that approximates the aspherical shape of the optical element that becomes the master mold, the resin shrinks when the shape difference between the mold and the substrate increases. This makes it difficult to obtain the accuracy of the manufactured aspherical optical element. At this time, the approximate value of the deviation in accuracy is obtained by multiplying the difference in shape by the curing shrinkage rate. For example, when a resin having a shape difference of 30 μm and a cure shrinkage rate of 2% is used, the accuracy deteriorates by 30 × 2 ÷ 100 = 0.6 μm only by cure shrinkage. Since this negative precision type is used as a negative mold and the inverted shape is taken again by the replica method, the surface accuracy of the product is further deteriorated.

  In order to solve this problem, when the product substrate itself is made into a rough aspherical surface as described in Patent Document 1, the manufacturing process becomes complicated compared to a flat or spherical surface even though it is a rough aspherical surface. Inevitably, using an aspherical substrate for all products is not a good idea in terms of cost.

  The present invention has been made in view of such circumstances, and a method for manufacturing an aspheric optical element with high accuracy at a low cost by using a master aspheric optical element and an approximate spherical or flat substrate. The purpose is to provide.

  In order to solve the above problems, in the method of the present invention, a replica method using a resin using an aspherical substrate having a shape that is concave and convex with respect to an aspherical optical element polished with high accuracy to be a master mold. The negative type was made. By doing so, the difference in the resin thickness between the master mold and the substrate becomes smaller than when a spherical surface is used for the substrate, and even if the resin is cured and contracted, the surface accuracy is hardly deteriorated.

As described above, the negative type substrate manufactured according to the present invention has an aspherical shape and the processing cost is slightly high. However, once the negative type is created by the replica method, it can be used over and over again. Compared with the conventional method in which the product substrate itself is aspherical, an aspherical optical element can be manufactured at a much lower price.
That is, the manufacturing method according to the present invention has an excellent effect that a more accurate aspherical optical element can be mass-produced at low cost.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 shows a process of manufacturing a negative mold 23 from a master mold 1. First, the surface of an aspherical optical element that has been polished with high accuracy to be the master mold 1 is treated with a release agent. Next, as shown in FIG. 1A, the resin layer 2 is sandwiched between the aspherical substrate 3 and the master mold 1 that are formed with an accuracy of 10 μm or less, and the resin layer 2 is cured by heat or light 6. As a result, the inverted shape of the master mold 1 is copied onto the surface of the resin layer 2 and the resin layer 2 and the aspherical substrate 3 are joined to form a negative mold 23.
After the resin layer 2 is cured, the negative mold 23 is separated from the master mold 1 as shown in FIG. 1B.

  In the above, by setting the deviation of the shape of the aspherical substrate 3 used as the base material of the negative mold 23 from the aspherical surface of the master mold 1 to 10 μm or less, it is possible to obtain practically sufficient accuracy. Processing the base material of the negative mold 23 with such accuracy can be easily achieved by using various processing machines.

FIG. 2 shows a process of manufacturing an aspherical optical element 45 as a product using the negative mold 23 manufactured as described above, and this process is basically the same as the conventional process.
That is, after the surface of the negative mold 23 is treated with a release agent as in the case of the master mold 1, the resin layer 4 is formed between the spherical or flat substrate 5 and the negative mold 23 as shown in FIG. 2A. The resin layer 4 is cured by sandwiching, heat or light 6. A combination of the cured resin layer 4 and the spherical surface or the flat substrate 5 is an aspherical optical element 45 manufactured according to the present invention. After the resin layer 4 is cured, the aspherical optical element 45 is separated from the negative mold 23 as shown in FIG. 2B.
Thus, the aspherical optical element 45 is manufactured by adding the resin layer 4 to the spherical surface or the surface of the flat substrate 5.

A method for manufacturing a glass lens in which one surface is a rotationally symmetric aspheric surface will be described.
First, an aspheric lens that is polished with high accuracy to be a master mold is prepared. A substance having releasability from the UV curable resin is laminated on the aspherical surface of the lens by dipping or vapor deposition. At this time, a protective layer may be provided between the release layer and the master in order to protect the surface.
Next, a master-type aspherical surface and an aspherical substrate having a shape in which the irregularities are reversed are manufactured by an NC lathe. At this time, the surface shape of the aspherical substrate is finished to a deviation of 10 μm or less from the master type aspherical surface, but it is not necessarily finished to a mirror surface.
A UV curable resin is dropped on the surface of the aspherical substrate, sandwiched by a master mold, and irradiated with UV light to cure the resin, and then the master mold and the aspherical substrate are separated. The surface of the aspherical substrate is reversely transferred to the surface of the master mold including the surface roughness by UV curable resin. Since the entire aspherical substrate is used as a negative type, a release layer is provided on the surface in the same manner as the master type.
Separately, a glass substrate having a spherical surface approximate to an aspherical surface is manufactured by a general polishing method, and the UV curable resin dropped on the negative surface is sandwiched between the spherical glass substrates, and the resin is cured by irradiating UV light. Let Thereafter, if the negative mold is separated from the spherical glass substrate to which the resin layer is bonded, an aspherical lens having the same shape as the master mold can be obtained.
When both surfaces are aspherical surfaces, the same process can be performed on both surfaces.

Next, a method for manufacturing an off-axis elliptical mirror will be described.
An off-axis ellipsoidal mirror polished with high accuracy to be a master mold is prepared, and gold is deposited on the surface of the master mold to form a release layer. Next, an off-axis elliptical substrate having an inverted shape of the master-type off-axis elliptical surface and the irregularity is manufactured by an NC grinder.
A thermosetting resin is dropped on the surface of the off-axis elliptical substrate, and is sandwiched and heated by the master type off-axis elliptical surface to cure the resin. Thereafter, the master mold and the off-axis elliptical substrate are separated. The surface of the off-axis elliptical substrate is reversely transferred to the surface of the master mold including the surface roughness by a thermosetting resin. In order to use the entire off-axis elliptical substrate as a negative type, gold is evaporated on the surface and a release layer is provided.
Subsequently, the metal material that becomes the substrate of the off-axis ellipsoidal mirror is made into a spherical shape approximate to the off-axis ellipsoid by machining.
A thermosetting resin is dropped on the negative surface, sandwiched between the spherical metal substrates and heated to cure the resin. Thereafter, the negative type and the spherical metal substrate are separated. An off-axis ellipsoidal mirror is manufactured by evaporating aluminum or gold on the thermosetting resin on the surface of the spherical metal substrate after separation.

  The manufacturing method of the aspherical optical element of the present invention is not limited to the above-described embodiments, and can be used in a wide range by adding various modifications without departing from the gist of the present invention.

Sectional drawing which shows the process in which a negative type | mold is manufactured from an aspherical master type | mold in this invention. Sectional drawing which shows the process in which the aspherical optical element used as a product is manufactured from a negative type in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Master type | mold 2 Resin layer 3 Aspherical board | substrate 4 Resin layer 5 Spherical surface or planar board | substrate 6 Heat or light 23 Negative type 45 Aspherical optical element

Claims (2)

A manufacturing method in which an aspherical optical element is manufactured by a replica method by adding a resin layer to a substrate surface having at least one surface that is spherical or flat, and is uneven with respect to a polished aspherical optical element that becomes a master mold A manufacturing method in which an aspherical substrate having an inverted shape is used as a negative base material to create a negative mold by a resin replica method, and an aspheric optical element is manufactured by using this negative mold by a resin replica method. 2. The method of manufacturing an aspherical optical element according to claim 1, wherein an aspherical substrate having a shape deviation of 10 [mu] m or less from the master type aspherical surface is used as the negative base material.

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